Migration

A primarily nocturnal, long-distance migrant, although may migrate diurnally to a greater extent than most other parulids, especially in fall (e.g., Duncan and Weber 1985). In e. U.S., a fairly early spring migrant and one of the earliest of all migrants in fall (Bent 1953, Leberman 1976, Peterjohn 1989, Sibley 1993). Populations breeding in Alaska and n. Canada may migrate later in both spring and fall than migratory populations breeding further south (Dunn and Garrett 1997). Evidence for a diurnal, circum-Gulf movement westward along n. Gulf coast in fall (Duncan and Weber 1985).

Spring

Migrants in Colombia recorded as late as early May (Hilty and Brown 1986), but usually depart Panama by end of Apr (Ridgely and Gwynne 1989, Wetmore et al. 1984); in Costa Rica “departs by early to mid-May” (Stiles and Skutch 1989: 388) and from Honduras by 10 May (Monroe 1968). Latest record for Oaxaca, Mexico, 23 May (Binford 1989). For Texas, extreme early arrival date 14 Mar; most migrants early Apr–late May (Oberholser 1974). Most northbound migrants apparently pass along the Mexico-Texas coast and cross w. Gulf of Mexico (Stevenson 1957); some may fly directly north from the Yucatán Peninsula, making landfall from Louisiana to Alabama (Bent 1953, Imhof 1976, Moore et al. 1990); others reach Florida (where the species is rare in spring), possibly via Cuba (Bent 1953, Stevenson 1957, Arendt 1992).

Overall, spring migration is prolonged, although rate appears to increase after arrival in s. U.S., from which main stem radiates north- and northeastward (Bent 1953). Transients present in Florida, Mar–May (Stevenson and Anderson 1994); in South Carolina, extreme dates 1 Apr–27 May (Sprunt and Chamberlain 1970). For Oklahoma, migrants present 11 Apr–1 Jun (Sutton 1967); for Kansas, late Apr–mid-May (earliest 11 Apr; most migrants between 20 Apr–26 May; Thompson and Ely 1992), for Iowa, early May to mid-May (earliest 24 Apr; Kent and Dinsmore 1996), and for Illinois, early Apr–late May (1 Apr exceptionally early, more normally arriving 14 Apr in s. Illinois, 19–20 Apr central Illinois, 24 Apr in n. Illinois; migration counts larger in w. Illinois than e. Illinois; Graber et al. 1983). For central Ohio, average arrival 22–26 Apr; for n. Ohio, 28 Apr–2 May (Peterjohn 1989); for w. Pennsylvania, 25 Apr (Leberman 1976, based on banding data).

Exceptionally large flights along western shore of Lake Erie in Ohio include 1,500 birds on 15 May 1948, 1,000 on 22 May 1943, 800 on 7 May 1983 (Peterjohn 1989); maximum recorded count in Cape May, NJ, of 100 birds on 26 Apr 1988 (Sibley 1993). Extreme early date in inland New York 19 Apr, bulk of migrants in early to mid-May (Bull 1974). In Massachusetts, frequently arrive on territory late Apr (earliest dates 6 and 17 Apr); 270 counted in Greater Springfield area 9 May 1970 (Veit and Petersen 1993); in Vermont, early to mid-May (Smith 1943, Kibbe 1985). Most male arrivals in s. Michigan last week of Apr, reaching Upper Peninsula mid-May (McPeek 1994). Median passage date in 1984–1986 in e.-central Minnesota 15 May (range 5–28 May), based on 26 mist net captures (Winker et al. 1992); statewide migration late Apr–late May (earliest 21 Apr; Janssen 1987). Most arrivals late May on southwestern coast of James Bay, Ontario, at 51°N latitude (earliest 25 May), main influx first 10 d of Jun (CCR). Arrives in early Jun at Churchill, Manitoba (mean date 7 Jun, earliest 3 Jun; Briskie 1995).

In w. U.S., migrants pass through se. Arizona mid-Mar, ne. Arizona mid-Jun (Phillips et al. 1964), San Diego Co., CA, late Mar–early Apr (Unitt 1984), nw. California mid- to late Apr (Dunn and Garrett 1997), n. Utah late Apr–mid-May (earliest males 29 Apr–4 May, most males by 7–8 May; Frydendall 1967); Oregon usual arrival late Apr, peak late May (earliest 2 Apr; Gilligan et al. 1994). First arrivals to s.-central British Columbia 10 Apr–19 May (median 11 May); arrival to central and n. British Columbia during first 10 d of May (Campbell et al. in press); for n. Idaho, first arrivals early May (as early as 30 Apr; Burleigh 1972); for nw. Montana, arrival 1 May–29 May (mean 12 May, n = 42; Weydemeyer 1973). Average arrival date of 8 May in se. South Dakota over 18 yr (earliest 24 Apr), most birds arrive second and third week of May (S. Dakota Ornithol. Union 1978). In central Alberta (Rumsey Ecological Reserve), first arrivals 15–22 May, with males continuing to arrive for about 15 d (CC). At Delta Marsh in s. Manitoba, arrival dates 10–20 May (Briskie 1995). Migrants arrive in interior of Alaska 16–24 May (Kessel 1989).

Fall

Fall migration of eastern populations among earliest of North American wood-warblers, underway by mid- to late Jul in much of eastern breeding range. Southern populations appear to depart earlier than those in north, probably due to earlier termination of breeding and Prebasic molt. Many migrants may go undetected because of early departure and inconspicuous behavior (e.g., Leberman 1976, Veit and Petersen 1993). Leaves Churchill, Manitoba, by mid-Aug (Jehl and Smith 1970). Migration of immatures peaks on southwestern coast of James Bay, Ontario, mid-Aug (latest 11 Sep), adults late Aug to early Sep (latest 8 Sep; Rimmer 1988). Fall passage in Minnesota late Jul–late Sep (latest 24 Oct; Janssen 1987), in Iowa mid-Jul to Sep (latest 5 Oct; Kent and Dinsmore 1996), in Kansas late Aug to mid-Sep (latest 14 Oct; most migrants between 20 Aug–25 Sep; Thompson and Ely 1992), in Michigan late Aug to late Sep (Sydlik 1991), in Vermont late Jul–early Aug, with occasional birds into mid-Sep (exceptionally 26 Oct; Kibbe 1985). Peak fall flights in Massachusetts during early Aug (Veit and Petersen 1993), in New York late Aug (extreme dates 11 and 24 Oct; Bull 1974). Fall flight at a w. Pennsylvania banding station shows very early peak of mid-Jul, with stragglers regularly through Aug and into Sep (latest date 1 Oct; Leberman 1976). Earliest of fall migrant warblers at Cape May, NJ, reported as early as 9 Jul, with fall maxima of 200 birds on 8 Aug 1989, 160 on 16 Aug 1988, and 120 on 2 Aug 1992 (Sibley 1993). Main southward migration in West Virginia during early Aug; few birds remaining by 1 Sep, although stragglers observed into Oct (Hall 1983). Transients recorded in S. Carolina 4 Jul–29 Oct (Sprunt and Chamberlain 1970). Fall migrants pass through Florida mid-Aug to mid-Oct (Stevenson and Anderson 1994), first appearing in northwestern panhandle mid-Jul, peaking there 1 Aug–10 Sep (Duncan and Weber 1985). Most birds in e. U.S. after Sep believed to be D. p. amnicola (Dunn and Garrett 1997).

Regular during fall in Bermuda, sometimes fairly common, most occurrences early Aug–late Sep (extremes 30 Jul–26 Nov); exceptional maximum of 68 on 15 Aug 1987 (Amos 1991).

Migration in w. North America ends later and is more protracted than in east, evident in late Jul, widespread by early Aug, peaking late Aug to early Sep (Dunn and Garrett 1997). In Alaska, “major movement” during first 3 wk of Aug (Kessel 1989); earliest migrants in British Columbia last week of Jul, peak passage middle 2 wk of Aug, extreme dates of 20 Oct inland, 9 Nov coastal (Campbell et al. in press). In Oregon, peak late Aug to early Sep, very few into Oct (Gilligan et al. 1994). Most migrants pass through n. Utah in late Aug (Frydendall 1967). In s. California, early migrants arrive late Jul to mid-Aug but most pass through during late Aug to late Sep (Small 1984); regularly remains in San Diego Co., CA, into mid-Oct, rarely Nov (Unitt 1984). In Arizona, fall migrants occur throughout Aug–early Oct, with following sequence of subspecies: D. p. sonorana (not past Sep), any race in Aug, D. p. rubiginosa and D. p. amnicola in Oct (Phillips et al. 1964). As in e. U.S., later fall migrants thought to represent more northerly subspecies (Dunn and Garrett 1997).

Transients recorded in Mexico by late Jul (Howell and Webb 1995); early date on Yucatán Peninsula 9 Aug (Rogers et al. 1986); earliest arrival in Oaxaca 20 Aug (Binford 1989). First arrivals in Costa Rica mid-Aug, peak migrant numbers Sep and Oct (Stiles and Skutch 1989). In Panama, few migrants arrive before late Aug (Ridgely and Gwynne 1989). Individual migrants recorded in South America as early as 26 Aug and as late as 24 Apr in Colombia, 1 Oct–3 May in Venezuela, and 2 Sep–14 Apr in Guyana (Paynter 1995).

Males arrive Michigan about 10 d before females (Kammeraad 1964), 9–10 d earlier in James Bay, Ontario (CCR), 4–5 d earlier in central Alberta (CC), but only 0–2 d earlier at Churchill, Manitoba (Briskie 1995). In Massachusetts, females arrived as early as males in 1 of 5 yr (DAS). Mean arrival dates of males at Prince Edward Point, Ontario, significantly earlier than those of females: 18.5 May ± 6.1 d SD (n = 271) and 20.2 May ± 5.0 (n = 164), respectively (Francis and Cooke 1986).

No consistent differences in timing or ratios of age classes among fall migrants. At James Bay, numbers of immatures peaked 10–14 d earlier than adults (Rimmer 1988); in New Jersey, migration of both age classes nearly synchronous (Murray 1966). Proportions of adults in banded and tower-killed samples ranged from 6% in coastal James Bay, Ontario (n = 768; CCR), to 15% in coastal New Jersey (n = 67; Murray 1966), to 77% in w. Minnesota (n = 74; Raveling and Warner 1978), to 86% at Long Point, Ontario (n = 763; Dunn and Nol 1980).

Fall observations of westbound migrants along northern Gulf Coast suggest diurnal, circum-Gulf migration (Duncan and Weber 1985); Aug records from Key West, Dry Tortugas, and e. Gulf of Mexico in-dicate some trans-Gulf movement in fall (Duncan and Weber 1985). Found more often in single- than in mixed-species flocks on Gulf Coast barrier islands following trans-Gulf flights in spring (Moore et al. 1990). No specific evidence of diurnal migration during spring.

Little information. Little evidence for deposi-tion of subcutaneous fat prior to spring and fall migrations, although body mass of adult males in Manitoba increased during the 5 wk before southward migration (Biermann and Sealy 1985; see Measurements: mass, below). Birds breeding at James Bay, Ontario, deposited no detectable pre-migratory fat and actually lost mass during late stages of remigial molt (Rimmer 1988).